The objectives of this research program are to develop a system for the quantitative assay of the permeability of the gingival crevicular epithelium; to analyze crevicular epithelial barrier components under a variety of physiological and pathological conditions; and to test the efficacy of several compounds in modifying crevicular permeability. An in vitro microassay system for determining the permeability of gingival sulcular epithelium has been devised. This system is reproducable and requires only a 2.0 mm punch biopsy of tissue for analysis. Recent studies indicate that the oral sulcular epithelium is significantly more permeable to radiolabelled dextran (mw 70,000) than the overlying Keratinized epithelium from the gingival margin. Future studies will be directed toward analyzing crevicular permeability in health and disease. BIBLIOGRAPHIC REFERENCE: "Prospective Improvements in the Prevention of Inflammatory Periodontal Disease." M,C,Alfano, J. Prev. Dent. 4: (in press) 1977